Method and apparatus for polishing flat glass



y 20, 1947- F. B. WALDRON 2,420,989

METHOD AND APPARATUS FOR POLISHING FLAT GLASS Filed March 50, 1945 12 /0o T 26 A I: x-Q 55A J \\\\\\\\x\\\\\\ i ff 27 l3 7 FIG. 3. 36a

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:3 y .L 2a A m *2 I I i a nvenor Attorneys.

Patented May 20, 1947 METHOD AND APPARATUS FOR POLISHING FLAT GLASSFrederic Barnes Waldron, Prescot, England, assignor to PilkingtonBrothers Limited, Liverpool, England, a British company ApplicationMarch 30, 1945, Serial No. 585,684 In Great Britain March 28, 1944 3Claims. 1 This invention relates to methods and apparatus for polishingflat glass.

In the usual apparatus for polishing fiat glass, pads are carried onsupports which are mounted on frames, so that the pads are free torotate on their axes, the frames rotating about axes normal to thesurface polished. The frames are either positively rotated, or they aremounted, so as to be free to rotate as subsidiary frames, on apositively driven central frame.

Pads are so located on their frames, that during the rotation of theframes, each pad at intervals passes over the edge of the glass.Usually, the pads are located so that about half the area of the padextends over the edge of the glass. The pads are sometimes mounted sothat they are capable of small angular movement relatively to the planeoftheir faces, whereby they arelfree to bed themselves on the glass.Also they are sometimes mounted on axes in a fixed direction, and thisdirection is either vertical or slightly inclined in such a directionthat, when a pad is extending over the edge of the glass, the edge ofthe pad beyond the glass is retracted from the plane of the surface ofthe glass. In the following description the pad will be said to betilted inwards when its outer edge, when overhanging the glass, is soretracted.

In the process of polishing, the rouge forms a layer on the surface ofthe pad, and this layer, when it is fresh and moist, is effective forpolishing. With continued operation, however, the layer thickens andbecomes hard and dry, and it is then less effective.

Devices have been employed for cleaning the pads, that is to say forremoving the layer which has become hard and dry, but they all entail aninterruption in the polishing process. In the case of continuouspolishing apparatus, in which the glass travels under or between asuccession of polishing tools, the interruption of the operation of atool is particularly harmful.

The main object of the present invention is to maintain the rouge on thepads of tools in a condition in which it is most effective forpolishing, without interrupting the polishing process carried out byapparatus employing a succession of tools as hereinbefore mentioned.

The present invention consists in a method of removing a layer of rouge,or the outer surface of such a layer from polishing pads during the polishing of flat glass, wherein the pads are periodically tiltedoutwardly, from their normal predetermined operative position to atemporary op erative position in which they intersect the plane of theglass surface being polished by the pads as the latter pass over theedge thereof so that the edge of the glass is employed to scrape rougefrom'the pads whilst they are so tilted, and, when 5 the said edge hasscraped the hard and dry rouge from the pads, they are returned to theirnormal operative position.

Apparatus for polishing flat glass according to the present inventioncomprises a plurality of polishing pads each carried on a disc rigidlymounted on a pin disposed as a normal to the respective disc, each saidpin being in turn connected by a support to a rotatable frame mounted torotate over the glass and cause each polishing pad to travel on theglass in a circularpath,

, characterised in that each pin support is constituted as a socket tohouse a pin and is mounted on the frame about a chordwise axis disposedin a plane parallel to the plane of the pads to be tiltable relativelyto the frame, setting means adapted to dispose each socket in apredetermined normal position for polishing, and means for actuatingsaid setting means during the rotation of the frame to outwardly tiltthe sockets from the said normal position to a predetermined tiltedposition, whereby the pads may be deflected from the normal position toa predetermined extent for the purpose specified and to return thesockets to normal position.

Preferably the said setting means includes an arm attached to eachsocket and extending inwardly of. the frame, and an axially displaceablemember carried by the frame and engaging the inner ends of all the armsoperatively connected to said actuating means.

The support may be hinged to the frame of the tool by employing a pivotpin, or since the tilting movement required is extremely small (lessthan one degree) the hinging of the support to the frame may be effectedby connecting the support to a flexible plate, in turn secured totheframe so that as the plate flexes the support is virtually hinged to theframe.

The invention is applicable to polishingappm ratus of the kind in whichthe glass is supp d on a table which carries the glass under a series ofpolishing tools, or to a polishing apparatus of the kind comprisingupper end lower co-axial polishing tools, between which the glass to be'polished passes as a ribbon and is supported by the lower tools andintermediate driving rollers, or to polishing apparatus of the kind inwhich the glass is carried on a rotating table.

From the foregoing it will be observed that a machine minder, watchingthe process of polishing glass carried out in apparatus of the kindreferred to, will, on seeing that the muse is becoming too dry, cause anoutward tilting of the polishing pads to be effected in order to removethe hard dryrouge layer from the polishing pads, and that when a pad isslightly tilted outwards,

the edge of the glass acts to scrape rouge from the pad, during thepassage of the pad over the edge. If then, during the polishingoperation, the pads are tilted outwards is described, the scrapingaction of the edge of the glass gradually removes the hard and drylayer, or the hard and dry part of the layer. The pads are thenuntilted, or preferably, tilted slightly inwards, and they are thenoperating in conditions favourable for taking up fresh rouge to form alayer which is effective for polishing.

Thus, by operating the polishing apparatus with the pads alternatelytilted outwards and in their normal operative position, the rouge on thepads is maintained in a condition which is effective for polishing,without any interruption of the polishing process.

In order that the invention maybe more clearly understood some preferredembodiments as incorporated in polishing apparatus including coaxialtools operating simultaneously on both faces of a ribbon of flat glassas it comes from the grinder, will now be described by way of exampiewith refemnce to the accompanying diagrammatic drawings, in which Figure1 is a fragmentary elevation, looking along the middle line of a ribbonof glass of a polishing tool, in which the hinge of the pad supportcomprises a pivot pin carried chordwise on the tool frame on the outsideof the pad support;

Figure 2 is a view similar to Figure 1 showing a modificationconsistingin the manner of hinging the support, and

Figure 3 is also a view similar to Figure 1.

In the drawings like references designate the same or similar parts.

Referring to Figure 1, the ribbon of glass l is polished by pads 2which, as is usual, are carried on discs 2a rotatably mounted on pins 2bcarried in supports 3. The support 3 is in nature a socket for the pin2b which is tiltable in a plane which is normal to the glass by beingpivoted at 4 about a chordwise axis to a bracket 5 depending from aframe 6 rotated by the central shaft 1. A rod 9, having bearing collarsI0, is adapted to slide vertically in a casing ll fixed centrally by aflange a to the lower surface of the frame 8. A bar l2 emanates fromeach support 3 and each bar has its end l3 engaged by the collars Ill,and each support takes its setting from the disposition of its bar sothat, when the rod 9 is moved upwards, the pad 2 is tilted outwardly inthe angular direction of the dotted line I, but only to an amountsomewhat less than 1.

The upward motion of the rod 9 is given by the hydraulic thrust deviceI5, of known type,

which has a limited travel which is attached to the frame 6. Whenhydraulic pressure is applied to the thrust device l5, the end l6 of itspiston rod turns the bar l1, pivoted at 18 on the casing H, in acounterclockwise direction. The end IQ of the bar I! inside the casingII is formed as a fork-straddling a flat on the rod 9, thus engaging ashoulder 20 on the rod. Counterclockwise rotation of the bar I!therefore moves the rod 9 upwards and outwardly tilts each pad 2operatively connected thereto in the same manner.

The pads operate at such a radius that during rotation they overhang theedges of the ribbon of glass; the amount of overhang, as shown,

is commonly about half the diameter of a pad 2. When a pad thus tiltedis overhanging the glass, its outer overhanging edge intersects theplane of the surface of the glass on which it is operating. The edge ofthe glass thus exercises a scraping action on the pad, as the pad, inits rotation, is brought fully on to the glass.

The amount of the tilt found suitable is too small to be shown in thedrawing, being of the order of onesixth of a degree, that is to say amere deflection of a polishing pad from the operative position. For apad 20 inches in diameter, this is equivalent to a lift or depression ofthe edge relatively to the centre of 0.03 inch; the surface of the pad,being yielding, does not therefore come out of contact with the glass;

For the normal polishing operation the pad may rest on the glass withits pin 2b in a vertical position, but preferably the pad is slightlytilted in the opposite direction to that shown by the line M. It mayalso be slightly tilted in the same direction as for cleaning the pads,but to a much less extent.

The parts may be so arranged that, when the piston of the thrust device[5 is in its home position shown, the pad occupies the desired normalangular position. This, however, may be made adjustable by means of thenuts 2| on the screw 22 fixed to the frame 6, the nuts engaging abracket 23 fixed to the bar 12 and thus limiting. the downward positionof the bar l2 at this point. Thereby, after the cleaning operation hasbeen effected, the pads are returned to the pristine angular positionfor normal operation.

In Figure 1, the tool is shown operating on the upper surface f a ribbonof glass of which the under surface is operated on simultaneously by asimilar tool which also serves to support the strip. The pads of thelower tool are then similarly mounted so as to be capable of beingtilted.

Figure 2 shows an alternative mounting of the pad 2. The support 3 isbolted at 24 to a strip of steel 25 which is flexible and is bolted to alug 26 on the frame 6. The bar l2 may either emanate from the support 3or, as shown, be connected to the strip 25. The thrust device, which maybe the same .asin the construction of Figure 1 is not shown for sake ofclarity in illustration. This form of pad mounting is not essentiallydifferent from that of Figure 1, since,

for the small turning movement, the pad is eflectively pivoted about achordwise axis.

The strip of glass I is shown on a table 21 of the form used incontinuous grinding ap aratus.

Figure 3 shows the invention ap lied to the form of polishing tool inwhich the pads are mounted on subsidiary frames free to rotate on acentral frame. The supports 3 are pivoted about chordwise axes as inFigure 1 to lugs 5 on the subsidiary frame 28, which is free to turn inthe central frame 6. The pads are tilted as in the constructionsdescribed with reference to Figures 1 and 2 by bars l2 engaged bycollars I on a rod 9 capable of upward movement centrally in thesubsidiary frame 28; The rod 9 extends above the frame 6 and has pivotedto it at 29 a bar 30 pivoted at 3| to a bracket 32 on the frame 6. Theother end of the bar 30 is engaged by collars 34 on a rod 35 adapted toslide downwards inthe centre of the frame 6.

The rod 35 is moved upwards, to outwardly tilt the pads. by an electricmotor 36 fixed to the frame 6 and provided with a reduction gear 36aadapted to rotate the screw 31. A nut 39 on the screw 31 has pivoted toit at 39 a bar 49 which is pivoted at 4| to a bracket 42 on the frame 6.The inner end of the bar 40 is forked and pivoted at 43 to a collar 44on the rod 35, engaged between a securing collar 45 and the lower collar34.

If the motor 33 be turned to move the nut 38 upwards, the rod 35, andthe right hand end of the bar 30, are moved downwards and consequentlythe rod 9 is lifted to tilt the pads in the desired outwardly direction.

Both the hydraulic thrust device and the electric motor 36 are operableby well known methods during the rotation of the polishing tool,

. and therefore the tilting of the pads can be effected withoutinterruption of the polishing operation.

The construction shown in Figures 1 and 2 permits the use of any desirednumber of pads to be carried on the frame 6, each pad being tiltable byreciprocation of the central rod 9. Similarly the construction shown inFigure 3 permits the use of any desired number of subsidiary frames,each carrying any desired number of pads. It is to be understood thatthe complete polishing apparatus comprises a plurality of toolsoperating in succession on the traveling glass.

In operation, the machine minder, on seeing that the rouge on the padsof any tool has become unduly hard and dry, will operate the tiltingdevice to tilt outwards all the pads of the tool. When the resultingscraping action by the edge of the glass has sufficiently cleaned thepads, he will operate the device toreturn the pads to their normalposition. And these operations will be effectedwithout interruption ofthe polishing process.

By the present invention standard forms of apparatus. at presentemployed for polishing sheet or plate glass may be modified to assurethat the rouge on each individual polishing pad is maintained in goodcondition for polishing, without interrupting the process of polishingcarried out by such forms of apparatus.

I claim:

1. In the polishing of flat glass by polishing pads each of which passesover the edge of the glass at intervals during the polishing operationand to which pads rouge is supplied, the method of removing hard and dryrouge from the polishing pads during the polishing operation, whereinthe pads are periodically tilted outwardly from 0 her carried by thetheir normal predetermined operative position to a temporary operativeposition in which they intersect the plane of the glass surface beingpolished by the pads as the latter pass over the edge thereof so thatthe edge of the glass is employed to scrape rouge from the pads whilstthey are so tilted, and, when the said edge has scraped the hard and dryrouge from the pads, they are returned to their normal operativeposition.

2. Apparatus for polishing flat glass comprising a plurality ofpolishing pads each carried on a disc rigidly mounted on a pin disposedas a normal to the respective disc, each said pin being in turnconnected by a support to a rotatable frame mounted to rotate over theglass and cause each polishing pad to travel on the glass in a circularpath, characterized in that each pin support is constituted as a socketto house a pin and is mounted on the frame about a chordwise axisdisposed in a plane parallel to the plane of the pads to be tiltablerelatively to the frame, setting means adapted to dispose each socket ina predetermined normal position for polishing, and mean for actuatingsaid setting means during the rotation of the frame to outwardly tiltthe sockets from the said normal position to a predetermined tiltedposition, whereby the pads may be deflected from the normal position toa predetermined extent for the purpose specified and to return thesockets to normal position.

3. Apparatus according to claim 2, characterized by the said settingmeans including an arm attached to each socket and extending inwardly ofthe frame, and an axially displaceable memframe and engaging the innerends of all the arms operatively connected to aid actuating means.

FREDERIC BARNES WALDRON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,548,105 Soderberg Aug. 4, 19251,872,694 Drake Aug. 23, 1932 1,934,797 Galey Nov. 14, 1933 1,836,542Miller Dec. 15, 1931 1,687,959 Waldron Oct. 16, 1928 1,854,507 DrakeApr. 19, 1932 1,922,912 Fox Aug. 15, 1933 1,928,196 Betrancourt Sept.26, 1933 2,372,824 Gould Apr. 3, 1945

